Forbes names 100 most powerful womenGerman Chancellor Angela Merkel tops list for the fourth consecutive yearAngela MerkelHerbert Knosowski / ASSOCIATED PRESSAt No. 1 on Forbes' most powerful women list, for the fourth consecutive year, is German Chancellor Angela Merkel. Up for reelection this September, she is leader of the world's fourth-largest economy.

Aug. 20: Forbes magazine’s Heidi Brown talks with TODAY’s Ann Curry about the women who ranked highest on the magazine’s annual list of the world’s most powerful women

Forbes' Power Women list isn't about celebrity or popularity; it's about influence. Queen Rania of Jordan (No. 75), for instance, is perhaps the most listened-to woman in the Middle East; her Twitter feed has 600,000 followers.

In assembling the list, Forbes looked for women who run countries, big companies or influential nonprofits. Their rankings are a combination of two scores: visibility — by press mentions — and the size of the organization or country these women lead.

At No. 1, for the fourth consecutive year, is German Chancellor Angela Merkel. Up for reelection this September, she is leader of the world's fourth-largest economy. She faces a tough year: Germany's GDP is expected to shrink this year despite a small uptick in the second quarter.

Federal Deposit Insurance Corp. Chairman Sheila Bair, who remains in the No. 2 spot, has presided over the orderly takeover of 77 banks so far this year. In fighting for more power for her agency, she has butted heads with Fed Chairman Ben Bernanke and U.S.Treasury Secretary Timothy Geithner.

Chief Executives Indra Nooyi of PepsiCo (No. 3), Cynthia Carroll of Anglo American (No. 4) and Irene Rosenfeld of Kraft Foods (No. 6) rank among the world's most powerful businesswomen and are tasked with steering their companies through unusually challenging times.

Singapore's sovereign wealth fund, Tamasek, has delivered extraordinary average annual returns of 18 percent under the leadership of Ho Ching (No. 5). She is currently seeking a successor.

This year's list includes several notable newcomers — from the U.S. and abroad. The recently approved Supreme Court Justice Sonia Sotomayor debuts at No. 54. She will be the third woman and the first Hispanic in the top court. First lady Michelle Obama, a champion for working women and the families of the U.S. military, appears at No. 40.

Among the female U.S. Cabinet secretaries, Homeland Security Secretary Janet Napolitano and Health and Human Services Secretary Kathleen Sebelius rank at No. 51 and No. 56, respectively. Meanwhile, SEC Chair Mary Schapiro (No. 55) is in the midst of a maelstrom, as Congress weighs new regulations of the financial services industry.

All eyes are also on Iceland's new prime minister, Johanna Sigurdardottir (No. 74) as she seeks to recapitalize the banks of her small island nation, which recently came very close to complete economic collapse. She is an advocate of Iceland's entry into the E.U. and adoption of the euro — views not entirely popular with her people.

In the tech sector, Carol Bartz (No. 12), who was appointed CEO of Yahoo! in January and is the former chief of Autodesk, faces tremendous pressure. With the Microsoft search deal behind her, she needs to show investors that she can quickly shore up the top and bottom lines.

An engineer by training, Ursula Burns (No. 14), was recently appointed CEO of Xerox, and is the first African-American woman to run a major U.S. public company.

This year, instead of including highly placed media figures, we spotlighted them with a list of their own.

To read the entire list of The 100 Most Powerful Women, visit Forbes.com